socketserver.TCPServer can not listen IPv6 address

[dazhaoyu]

BPO	20215
Nosy	@gpshead, @jaraco, @nirs, @giampaolo, @bitdancer, @berkerpeksag, @vadmium, @jleedev
PRs	bpo-38907: In http.server script, restore binding to IPv4 on Windows. #17851
Files	issue20215_socketserver.patch: Patch against latest Python 3.5 mercurial branch issue20215-gps01.diff

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2014-01-10.02:03:02.342>
labels = ['type-feature', 'library']
title = 'socketserver.TCPServer can not listen IPv6 address'
updated_at = <Date 2020-01-06.02:11:41.352>
user = 'https://bugs.python.org/dazhaoyu'

bugs.python.org fields:

activity = <Date 2020-01-06.02:11:41.352>
actor = 'jaraco'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2014-01-10.02:03:02.342>
creator = 'dazhaoyu'
dependencies = []
files = ['35147', '43983']
hgrepos = []
issue_num = 20215
keywords = ['patch']
message_count = 14.0
messages = ['207818', '207824', '217833', '226219', '231363', '231377', '231379', '243884', '271865', '271869', '271871', '271872', '271873', '325416']
nosy_count = 14.0
nosy_names = ['gregory.p.smith', 'jaraco', 'nirs', 'giampaolo.rodola', 'r.david.murray', 'neologix', 'berker.peksag', 'martin.panter', 'jpokorny', 'jleedev', 'dazhaoyu', 'andreasr', 'Carlos.Ralli', 'Paul Marks']
pr_nums = ['17851']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue20215'
versions = ['Python 3.5']

Linked PRs

• gh-64414: mention AF_INET6 and IPv6 in socketserver docs. #129866
• [3.13] gh-64414: mention AF_INET6 and IPv6 in socketserver docs. (GH-129866) #129868
• [3.12] gh-64414: mention AF_INET6 and IPv6 in socketserver docs. (GH-129866) #129869

[dazhaoyu]

I see, in python 2.7, in SocketServer.py the TCPServer implementation is hard-coded to use ipv4, can not handle IPv6 case. it hard-coded set address_family as socket.AF_INET. so when binding IPv6 host, it will throw "gaierror: [Errno -9] Address family for hostname not supported".

The code should to judge the provided host is IPv4 or IPv6, and base on the host type to set address_family as socket.AF_INET or socket.AF_INET6

[bitdancer]

The *default* is AF_INET. If you are requesting a more convenient API than subclassing (which for IPV6 support I think would be a reasonable request), that would be a new feature.

[andreasr]

Here's a patch which implements support in SocketServer to set IPv6 socket address family to AF_INET6 automatically if the TCPServer is specified to listen to an IPv6 address. This means that users of the TCPServer class will get the correct address family automatically for both IPv4 and IPv6 based on the IP address they specify, and hopefully this will be more userfriendly. The patch is against the latest Python 3.5.

Note that this is my first patch to the Python project, I hope I did everything correct.

[andreasr]

Is there any interest in this patch? it would be nice with a review of the patch. :)

[CarlosRalli]

Is it possible to use this patch for python2.7 ?

[CarlosRalli]

Sorry, I've got nothing. Did you forget the attachment or mail body ?

2014-11-19 11:08 GMT+01:00 Berker Peksag <report@bugs.python.org>:

Changes by Berker Peksag <berker.peksag@gmail.com>:

----------
nosy: +berker.peksag
stage: -> patch review

---

Python tracker <report@bugs.python.org>
<http://bugs.python.org/issue20215\>

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[bitdancer]

Andreas: I would prefer to avoid a dependency on the ipaddress module. I would suggest adding an address_family constructor argument that defaults to None, where a value of None would mean "just pass the server_address to bind (or getaddrinfo?) and find out what the resulting family is". I'm not exactly a socket programming expert, though, so there may be a reason I'm not aware of that that won't work well.

Carlos: no, this is a new feature, so it can go into 3.5 only at this point.

[vadmium]

I’m no IPv6 expert, but see Lib/smtpd.py:657 and bpo-14758 for how this sort of thing was done for the SMTP server using getaddrinfo(). I think it is similar to David’s suggestion.

I also left a comment about the documentation. And it probably needs a test case as well.

[gpshead]

TL;DR - We really need reliable tests for the exact behavior we want before coming up with patches.

attached is a patch (-gps01) that would do the same thing as Lib/smtpd.py does... But I'm not convinced it is a good idea.

Would forcing a socket.getaddrinfo() call from the constructor cause problems? This would be new behavior over what TCPServer did in the past. Could it trigger a blocking reverse DNS lookup where there wasn't one in the past?

What about when server_address[0] is ''? getaddrinfo() fails on that, but the existing code works and binds to 0.0.0.0. Presumably this should bind via AF_INET6 if the host supports it but a simple getaddrinfo() call doesn't tell us that.